1. Field of the Invention
This invention relates generally to a video tape recorder (VTR) and to a motor servo system suitable for use in a VTR of the rotary magnetic head type. More particularly, but not exclusively, the invention relates to a battery-operable, portable VTR.
2. Description of the Prior Art
A servo-driven drum motor of a rotary head type VTR is normally connected to a motor drive amplifier of a servo system. Even during the pause mode of the VTR, the drum motor remains connected to the motor drive amplifier and so rotates at high speed. For a battery-operable VTR, such operation is very disadvantageous, due to the large electric power consumption. However, if in the pause mode the power supply to the drum motor is interrupted to stop the drum motor, the magnetic tape sometimes sticks to the rotary head drum due to the tension under which the magnetic tape is maintained so that the drum motor may be prevented from restarting or the magnetic tape may snap when the drum motor restarts.
Moreover, it is usual in a VTR for the tape transport system to only advance the magnetic tape when an input video signal is present during the recording mode to minimize the amount of magnetic tape used. In the absence of an input video signal to be recorded, the VTR is in the pause mode and no magnetic tape transport is effected. However, after release of the pause mode by the input video signal, it usually takes 1 to 2 seconds for the servo system to become locked, during which period the magnetic tape is advanced and used wastefully.